V4L/DVB (5982): Dev.c: memset fix

Looks like memset() is zeroing wrong nr of bytes.
Signed-off-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/videodev.c

@@ -448,7 +448,7 @@ static int __video_do_ioctl(struct inode *inode, struct file *file,
 	if (cmd == VIDIOCGMBUF) {
 		struct video_mbuf *p=arg;
 
-		memset(p,0,sizeof(p));
+		memset(p, 0, sizeof(*p));
 
 		if (!vfd->vidiocgmbuf)
 			return ret;